1) Barely cook 2) Cook less than needed 3) Cook rare 4) Not cook enough 
• (v. i.) To do less than is requisite or proper; -- opposed to overdo. • (v. t.) To do less thoroughly than is requisite; specifically, to cook insufficiently; as, to underdo the meat; -- opposed to overdo.
to do less or in a lesser fashion than is usual or requisite.